As is well known, magnetic recording methods are classified generally into two kinds of modes. The first one is a recording mode utilizing the longitudinal residual magnetization to the surface of the recording medium, while the other is a mode utilizing the perpendicular residual magnetization. The former longitudinal magnetic recording method has long been employed, but investigation and development of the latter perpendicular magnetic recording mode have been widely continued because this latter method provides higher recording density as compared with the longitudinal recording method.
As to this perpendicular recording mode, the systems as indicated in FIG. 1 and FIG. 2 are currently known.
Namely, known is the perpendicular magnetic recording system comprising a magnetic head obtained by providing a main pole piece 2, as indicated in FIG. 1, perpendicular to the magnetic recording medium, where the Co-Cr alloy film having the magnetic anisotropy in the perpendicular direction is provided on a plastic or aluminium base material 3, and by forming a coil 1' around said main pole piece 2.
This recording system is generally called the main pole excitation system. Also known is the perpendicular magnetic recording system having a magnetic head, as indicated in FIG. 2, where the main pole piece 2 and the auxiliary pole piece 4 are provided perpendicular to the magnetic recording medium as indicated in FIG. 1 mutually facing the medium and a coil 1' is formed around the auxiliary pole piece 4. This system is generally called the auxiliary pole excitation system. In such perpendicular magnetic recording systems, the perpendicular magnetic recording is carried out as indicated in FIGS. 1 and 2 on the recording medium by exciting the coil 1' of the magnetic head.
Such perpendicular recording systems, however, have the disadvantages as explained below.
Namely, in the perpendicular recording system employing the main pole excitation method indicated in FIG. 1, this main pole piece 2 itself determines the recording density of the medium and is designed in a very small size. Therefore, it is difficult to form a coil having a large number of turns to said main pole piece 2, and resultingly it cannot generate an intensified magnetic field.
In addition, since the coil is formed around this main pole piece 2, it cannot be formed in a large size because it would be difficult to generate a sharp magnetic field for the recording medium.
Moreover, a thin film magnetic head has been employed recently in order to miniaturize the magnetic head, but if formation of such a magnetic head using a thin film head is attempted, formation of the coil will become difficult and the manufacturing processes will also be complicated.
On the other hand, in the case of the auxiliary pole excitation system indicated in FIG. 2, recording is carried out on the recording medium by concentrating the magnetic flux generated by the auxiliary pole 4 to the main pole 2. The recording efficiency is rather bad, however, because the magnetic film of the recording medium 1 and the magnetic field generation position are apart. Moreover, the coil 1' has a large inductance and it is difficult to drive such a magnetic head at a high speed.
Since the main pole 2 and the auxiliary pole 4 are provided face to face on both sides of the recording medium, this system also cannot be used for magnetic recording systems using a thick substrate recording medium, such as a magnetic disk unit.